1. Field of the Invention
The present invention is related to media control and, more specifically, media control valves used to control the flow of a media into a fluid stream as part of an apparatus for treatment of a surface, and is particularly directed to a remote ON/OFF type media control valve with manual abrasive flow metering.
2. Description of the Related Art
A typical media control valve is disclosed in U.S. Pat. No. 3,476,440 (“the '440 patent”), which is hereby incorporated by reference in its entirety. The valve of the '440 patent is attached to a media vessel and controls the flow of the media from the media vessel into a conduit containing a fluid stream. This conduit terminates in a nozzle. Fluid and media pass through the nozzle at high speed and are typically used to treat surfaces.
Over the years many modifications to media control valves have been proposed. For example, U.S. Pat. No. 5,810,045 (“the '045 patent”) discloses a valve for introducing particulate materials into a high-pressure air stream and suggests several uses for this valve. For example, the '045 patent suggests that the valve may be used for purposes such as introducing fluid catalytic cracking catalyst particles into fluid catalytic cracking units used to crack and reform various petroleum based products, introducing particulate catalysts into other kinds of chemical processes and spraying particulate ingredients on adhesive substrates as part of various manufacturing processes. U.S. Pat. No. 5,407,379 (“the '379 patent”) and U.S. Pat. No. 5,401,205 (“the '205 patent”) disclose a media control valve having a media passage between the media control valve and the conduit. The media passage converges into a slot-shaped outlet in the conduit so as to reduce the perimeter of the outlet placed perpendicular to air flow and consequently reduce turbulence as air passes across the outlet. The '045 patent also includes the use of multiple seals around a plunger of the valve with an exhaust therebetween to remove any contaminants that breach the seals.
One of the most critical issues with media control valves is the life of the valve. The abrasive media can damage the valve beyond use in a short period of time, requiring replacement or substantial repair. The valves of the prior art, as particularly shown in the '440 and '045 patents, typically have a sleeve that consists of a hardened liner (tungsten carbide or hardened steel) jacketed with a softer material. In these configurations, the hard liner is jacketed and bonded with stainless steel with the ID of the jacket being flush with the ID of the hard liner. The valve plunger is of the same type construction, except that the jacket is a hard material and the inside is a softer more workable material. It is not uncommon for any of these valves to malfunction after some use due to the sleeve and plunger locking up, thereby not allowing the plunger to reciprocate within of the sleeve. When plungers lock up or seize, accelerated wear is resulted on the adjacent components of the valve such as the body, seat, and base.
The '045 patent purports to keep particulates from entering the cylinder chamber, and thereby improve the life of the valve. However, this patent does not address the more frequent mode of failure where the plunger binds against the sleeve. Further, the statement that the '045 design of the plunger and sleeve block the migration of particles past the assembly simply is not correct. A gap is required for assembly of the plunger into the sleeve. Even with a gap of 0.001″ gap particles will migrate past the gap.
The design of the prior art would experience frequent seizing or locking up between the plunger and the sleeve jacket ID, which is designed to machine flush with the ID of the hard liner. After years of extensive experimentation and study it has been determined that this seizing can be attributed to several factors. First, the stainless jacket on the sleeve wears at the ID more quickly than at the hard liner primarily because of the difference in hardness of the two materials. This creates a beveled surface between the sleeve stainless ID and plunger OD where particles would cause binding. In addition, the stainless ID section of the sleeve is softer than some of the abrasive media used, such as aluminum oxide grit or hardened steel grit. These harder particles can dig into the relatively softer yet still rigid stainless steel and cause binding between the plunger and sleeve.
There is a need for a valve system having a longer life in order to increase the efficiency of the overall system.